This invention relates generally to downhole cutting tools and cleaning methods and more particularly, but not by way of limitation, to clean-out tools having enhanced stability and including longitudinal fluid channels defined therethrough and used a method for removing material from a tubular string and/or a borehole.
Casing fixed downhole in a well bore sometimes needs to be cleaned of cement, sand, shale, mud and other types of deposits as is known in the oil and gas industry. This requires a type of tool which can be lowered through a relatively narrow diameter tubing string to clean the tubing string and which can be lowered for subsequent use to clean below the lower end of the tubing string in the relatively wider diameter casing. This type of tool will be referred to herein as an enhanced diameter clean-out tool, or simply a clean-out tool. An early form of such a clean-out tool which has been in commercial use is disclosed in my U.S. patent application Ser. No. 888,418, filed July 23, 1986, now abandoned.
Other types of tools have been disclosed to include blades which are to be retracted within the support portion of the tool so that the blades and the tool can pass through tubing string having an inner diameter smaller than the maximum diameter of the blades when they are extended. Once having passed through the tubing string, the blades can be extended outwardly to cut out a diameter up to substantially the inner diameter of the casing or other borehole surface within which the tool is used.
It is my understanding that some tools which have been proposed or used have utilized springs to extend or retract the blades or have otherwise been mechanically operated to achieve the movement of the blades between their extended and retracted positions. Pistons moved by pressurized fluid have also been used to extend the blades. Some of these tools also have had jet ports through which fluid can be ejected to assist in cutting the material and in subsequently flushing the cut material out of the well. Others use ports which are opened to pressure-affecting fluid flow in response to the blades being extended.
Larger diameter tools of a generally similar type have been used in the cutting and parting of casing strings but these have not been of a type that can be passed through smaller diameter tubulars.
I am also aware of a pipe or casing cutter which cuts pipe or casing at its outer point and not along its side edges. A specific type of cutter of which I am aware is a Bowen internal pressure pipe cutter having a plurality of knives each separately pivotally connected within a body in which a piston is also disposed. The piston is used to drive the blades outwardly to apply pressure by which a pipe is cut.
A formation notching apparatus including two sets of cutting elements is disclosed in U.S. Pat. No. 3,050,122.
Although there are various types of downhole cutting devices, there has existed the need for an improved clean-out tool which has enhanced stability so that it can be used effectively, without substantial vibrations being created, on what is known as a coil tubing motor. An example of one such motor is known as a SLIMDRIL motor marketed by SlimDril, Inc. of Houston, Tex. There has also existed the need for an improved clean-out tool which provides significant liquid flow longitudinally through it for washing out, or otherwise lubricating, cuttings but which also generates through such liquid flow signals indicating when the extendible elements of the tool have opened.